(19) |
|
|
(11) |
EP 1 620 665 B1 |
(12) |
EUROPEAN PATENT SPECIFICATION |
(45) |
Mention of the grant of the patent: |
|
28.07.2010 Bulletin 2010/30 |
(22) |
Date of filing: 07.05.2004 |
|
(51) |
International Patent Classification (IPC):
|
(86) |
International application number: |
|
PCT/GB2004/001976 |
(87) |
International publication number: |
|
WO 2004/099654 (18.11.2004 Gazette 2004/47) |
|
(54) |
METHOD FOR PERFORMING A KICKDOWN SHIFT IN A TRANSMISSION SYSTEM
VERFAHREN ZUR DURCHFÜHRUNG VON KICKDOWN-SCHALTUNG IN EINEM GETRIEBE
METHODE POUR REALISER UN KICKDOWN COMMANDE POUR UNE TRANSMISSION
|
(84) |
Designated Contracting States: |
|
AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HU IE IT LI LU MC NL PL PT RO SE SI SK TR
|
|
Designated Extension States: |
|
AL HR LT LV MK |
(30) |
Priority: |
07.05.2003 GB 0310482
|
(43) |
Date of publication of application: |
|
01.02.2006 Bulletin 2006/05 |
(60) |
Divisional application: |
|
06023007.5 / 1748231 |
(73) |
Proprietor: Zeroshift Limited |
|
Knowlhill
Milton Keynes MK5 8PB (GB) |
|
(72) |
Inventor: |
|
- Martin, William Wesley
Milton Keynes (GB)
|
(74) |
Representative: Raynor, Simon Mark et al |
|
Urquhart-Dykes & Lord LLP
Midsummer House
413 Midsummer Boulevard Central Milton Keynes MK9 3BN Central Milton Keynes MK9 3BN (GB) |
(56) |
References cited: :
WO-A-01/29440 DE-B- 1 450 177
|
DE-A- 2 324 801
|
|
|
|
|
|
|
|
|
Note: Within nine months from the publication of the mention of the grant of the European
patent, any person may give notice to the European Patent Office of opposition to
the European patent
granted. Notice of opposition shall be filed in a written reasoned statement. It shall
not be deemed to
have been filed until the opposition fee has been paid. (Art. 99(1) European Patent
Convention).
|
[0001] The present invention relates to a method for performing a kick down shift in a transmission
system, according to the preamble of claim 1.
[0002] A known dog-type transmission system is described in
WO 01/29440. The transmission system disclosed in that document is particularly suited for use
in racing vehicles. When changing gear using conventional manual gearboxes there is
a torque interruption when a first gear is disengaged and a second gear is selected.
In racing vehicles it is necessary to reduce torque interruption time to a minimum
thereby maximizing the amount of time an engine drives the vehicle. Torque interruptions
lasting tenths of a second between gear changes can have significant impact on a vehicle's
performance and hence placing in a race. The transmission system of
WO 01/29440 addresses this problem by using dog rings engageable with recess rings attached to
first and second gears mounted on an input shaft, and an actuator for moving the dog
rings into and out of engagement with the recess rings, such that the first gear is
still engaged when the second gear is selected, thereby reducing the torque interruption
time to nearly zero.
[0003] Conventional gearboxes use synchronising cones to reduce the amount of backlash experienced:
however these have the drawback that torque interrupts are relatively long when changing
gear. Large torque interrupts affect the efficiency of the vehicle, and in particular
lead to increased fuel consumption and higher emissions.
[0004] One problem with the invention disclosed in
WO 01/29440 is that significant backlash occurs when accelerating or decelerating in a particular
gear. The backlash is acceptable to racing drivers since racing drivers are generally
more skilled than road users and are more interested in vehicle performance rather
than obtaining a smooth ride. Therefore the advantage of reducing the duration of
torque interrupts provided by the invention of
WO 01/29440 for racing drivers far outweighs the backlash experienced. However, with regards
to conventional road vehicles such as cars and motorcycles a smooth ride is a more
important criterion and therefore transmission systems with large amounts of backlash
are unsuitable for the vast majority of vehicles.
[0005] Furthermore, the invention of
WO 01/29440 uses a spline configuration that leads to structural weakness and which requires
the dog rings to be very strong to prevent them from breaking apart under operating
conditions. A further structural weakness is the cantilevered configuration of the
recess rings. Also the arrangement of the arcuate recesses formed in the ring causes
problems for the dog rings to properly engage with the gear wheels.
[0006] The actuator assembly is also bulky leading to large gear boxes.
[0007] Other transmission systems have used roller clutches or pawl engagement systems.
In the latter case, the pawl mechanism is mounted in a cavity in a shaft. Engagement
mechanisms mounted internally in shafts are very complex and difficult to assemble
and as such have proved to be commercially unviable.
[0008] According to one aspect of the invention there is provided a method of performing
a kickdown shift according to claim 1.
[0009] The type of transmission system to which the method is applicable performs accelerating
upshifts and braking down-shifts substantially without torque interruption. When performing
kickdown shifts (accelerating downshifts), there is a brief torque interruption prior
to the shift.
[0010] Preferably the first shaft is an input shaft and the second shaft is an output shaft
and drive is transferred from the input shaft to the output shaft. Alternatively,
the first shaft can be the output shaft and the second shaft is the input shaft.
[0011] Preferably the selector assembly is arranged such that when a braking force is transmitted
the first set of engagement members drivingly engages the engaged gear wheel, and
the second set of engagement members is in an unloaded condition, and when a driving
force is transmitted the second set of engagement members drivingly engages the engaged
gear wheel, and the second set of engagement members is then in an unloaded condition.
[0012] Advantageously the actuator assembly is arranged to bias the loaded set of engagement
members towards the unengaged gear wheel without disengaging the loaded set of engagement
members from the engaged gear wheel.
[0013] Preferably the first and second sets of engagement members are arranged to rotate,
in use, with the first shaft. The selector assembly is arranged such that the first
and second sets of engagement members can move axially relative to each other along
the first shaft. The first and second sets of engagement members are axially aligned
when both sets engage the first or second gear wheels, and preferably when in a neutral
condition. The first and second sets of engagement members are axially offset during
gear change operations.
[0014] The selector assembly is arranged such that when the first and second sets of engagement
members engage one of the first and second gear wheels the backlash when moving between
acceleration and deceleration is less than or equal to four degrees.
[0015] Advantageously the drive formations on the first and second gear wheels comprise
first and second groups of dogs respectively. The first and second groups of dogs
each comprise between two and eight dogs, evenly distributed on the first and second
gears respectively. Preferably the first and second groups of dogs each comprise between
two and four dogs, and preferably three dogs.
[0016] Preferably the drive formations on the first and second gear wheels do not extend
beyond the outer diameter of the gear wheels.
[0017] Advantageously the first and second sets of engagement members comprise between two
and eight members. Preferably the first and second sets of engagement members comprise
between two and four members, and preferably three members.
[0018] Advantageously the first shaft includes keyways formed in its curved surface arranged
such that the first and second sets of engagement members can slide axially along
the keyways and to radially restrain the positions of the sets of engagement members.
Preferably the cross-section of the keyways is one of T-shaped, slotted, and dovetailed.
[0019] Advantageously the actuator assembly includes at least one resiliently deformable
means arranged to move at least one of the first and second sets of engagement members
into engagement with the first and second gear wheels when the engagement members
are in unloaded conditions. The at least one resiliently deformable means is arranged
to bias at least one of the first and second sets of engagement members towards the
first or second gear wheel when the engagement members are drivingly engaged with
a gear wheel.
[0020] Preferably, the actuator assembly includes first and second resiliently deformable
means connected to the first and second sets of engagement members respectively such
that the first resiliently deformable means acts on the first set engagement members
and the second resiliently deformable means acts on the second set engagement members.
[0021] In one embodiment the at least one resiliently deformable means is connected to the
first and second sets of engagement members such that the resiliently deformable means
acts on both the first and second sets of engagement members.
[0022] In embodiments including dovetailed or slotted keyways, the members of the first
and / or second sets of engagement members can perform limited axial movement relative
to each other in the keyways.
[0023] Advantageously the resiliently deformable means is a spring, and preferably a disc
spring. Preferably the disc spring includes a plurality of arms, each arm having a
first part that extends circumferentially around a portion of the disc spring and
a second part that extends substantially radially inwards.
[0024] Preferably the actuator assembly includes a fork that is arranged to engage the resiliently
defonnable means to move it axially along the first shaft.
[0025] The transmission system may further include third and fourth gears mounted on the
first shaft and a second selector assembly to provide additional gear ratios between
the first and second shafts.
[0026] An embodiment of the present invention will now be described, by way of example only,
with reference to the accompanying drawings in which like references indicate equivalent
features, wherein:
Figure 1 is a general arrangement of a transmission system in accordance with the
present invention;
Figure 2 is a perspective view of part of a selector assembly;
Figure 3 illustrates the arrangement of a group of dogs on a side of a gear;
Figure 4 is a plan of a disc spring;
Figures 5a-f illustrate diagrammatically operation of the selector assembly;
Figure 6 is a sectional view of an input shaft; and
Figure 7 is a plan view of a disc spring for a second embodiment of the invention.
[0027] Figure 1 shows a transmission system in accordance with the invention. The transmission
system comprises an input shaft 1 having first and second gear wheels 3,5 mounted
thereon, an output shaft 7 having third and fourth gear wheels 9,11 mounted thereon
and a selector assembly 13. The first and second gear wheels 3,5 are rotatably mounted
on the input shaft 1 and the third and fourth gear wheels 9,11 are fixedly mounted
on the output shaft 7. The first and second gear wheels 3,5 mesh with third and fourth
gear wheels 9,11 respectively to form first and second gear wheel pairs 15,17.
[0028] Rotational drive may be transferred from the input shaft 1 to the output shaft 7
via either the first or second gear wheel pairs 15,17, with selection of the gear
wheel pairs being determined by the position of the selector assembly 13. The selector
assembly 13 engages first and second groups of drive formations 19,21 located on the
first and second gear wheels 3,5 respectively. The drive formations each comprise
groups of dogs.
[0029] The first dog group 19 is located on one side of the first gear wheel 3. The dogs
are preferably formed integrally with the first gear wheel, but this is not essential.
The first dog group 19 comprises three dogs evenly circumferentially distributed about
the gear face, i.e. the angle subtended between the centres of a pair of dogs is approximately
120° (see Figure 3). The second dog group 21, comprises three dogs and is similarly
arranged on one side of the second gear wheel. Three dogs are used because this arrangement
provides large engagement windows, that is the spaces between the dogs, to receive
the selector assembly 13. Large engagement windows provide greater opportunities for
the selector assembly to fully engage the gear wheels 3,5 before transmitting drive
thereto. If the selector assembly 13 drives a gear wheel when only partially engaged
it can lead to damage of the dogs and / or the selector assembly 13.
[0030] The first and second gear wheels 3,5 are mounted spaced apart on the input shaft
1 on roller bearings 23,25 and are arranged such that the sides including the first
and second dog groups face each other.
[0031] The selector assembly 13 includes first and second sets of engagement bars 27,29
and an actuator assembly 31 in the form of a fork assembly 33 and a selector rod 35.
[0032] The first and second sets of engagement bars 27,29 are mounted on the input shaft
1 between the first and second gear wheels 3,5. Referring specifically to Figure 2,
the first set of engagement bars 27 comprises three bars 28 attached to a first connector
ring, for example using grub screws. The first connector ring 37 holds the bars in
a fixed arrangement. The bars 28 are evenly distributed about the inner circumference
of the first connector ring such that their bases face inwards, and the bars 28 are
arranged substantially parallel. The second set of engagement bars 29 comprises three
bars 30 which are held in a similar fixed arrangement by a second connector ring 39.
[0033] The first and second engagement bar sets 27,29 are mounted on the input shaft 1 between
the first and second gear wheels 3,5. The sets of engagement bars 27,29 are arranged
to rotate with the input shaft 1 but are able to slide axially along the shaft in
response to a switching action of the actuator assembly 31. To facilitate this, the
input shaft 1 includes six keyways 41 formed in its curved surface with each engagement
bar 28,30 having a complementary formation in its base. The arrangement of the bar
sets 27,29 is such that bars of a particular set are located in alternate keyways
41 and the bar sets 27,29 can slide along the input shaft 1. Each bar set 27,29 moves
as a unit and each bar set can move independently of the other. When there is relative
movement between the first and second sets ofbars 27,29, the second connector ring
39 slides over the first set of bars 27 and the first connector ring 37 slides over
the second set of bars 29.
[0034] Each bar 28 in the first bar set 27 has a first end 28a arranged to engage the first
group of dogs 19 attached to the first gear wheel 3 and a second end 28b arranged
to engage the second group of dogs 21 on the second gear wheel 5. The first and second
ends 28a,28b typically have the same configuration but are opposite handed, such that
the first end 28a is arranged to engage the first group of dogs 19 during deceleration
of the first gear wheel 3 and the second end 28b is arranged to engage the second
group of dogs 21 during acceleration of.the second gear wheel 5, for example during
engine braking in automotive applications. Each bar 30 in the second bar set 29 is
similarly arranged, except that the first end 30a is arranged to engage the first
group of dogs 19 during acceleration of the first gear wheel 3 and the second end
30b is arranged to engage the second group of dogs 21 during deceleration of the second
gear wheel 5.
[0035] When both the first and second sets of engagement bars 27,29 engage a gear wheel
drive is transmitted from the input shaft 1 to the output shaft 7 whether the gear
is accelerating or decelerating.
[0036] The first and second ends 28a,30a,28b,30b of each bar include a substantially vertical
face 43 for engaging dogs 19,21 and a ramp 45 that slopes in the direction of the
engagement face 43 to ensure that the bars 28,30 disengage from the dogs 19,21 to
prevent the transmission from locking up. When the bars of the first and second sets
27,29 are interleaved, as in Figure 2, the dog engagement faces 43 of the first end
28a of the first set of bars 27 are adjacent the dog engagement faces 43 of the first
end 30a of the second set of bars 29. When the first and second sets of bars 27,29
are fully engaged with a gear a dog is located between each pair of adjacent engagement
faces 43. The dimensions of the dogs 19,21 and the ends of the bars are preferably
such that there is little movement of a dog between the engagement face 43 of the
acceleration bar and the engagement face 43 of the deceleration bar when the gear
moves from acceleration to deceleration, or vice versa, to ensure that there is little
or no backlash in the gear.
[0037] Preferably the bars are configured to be close to the input shaft 1 to prevent significant
cantilever effects due to large radial distances of loaded areas thus reducing the
potential for structural failure.
[0038] The actuator assembly 31 is arranged such that the fork assembly 33 is mounted on
the selector rod 35, and the selector rod is provided parallel to the input shaft
1 and adjacent thereto. The fork assembly 33 includes a fork 46 and first and second
annular disc springs 47,49 mounted about the input shaft 1 (see Figure 1). The first
and second disc springs 47,49 have three arms, with each arm having a first part that
extends circumferentially around a part of the spring and a second part that extends
radially inwards (see Figure 4).
[0039] The fork 46 has a first pair of arcuate members 51 arranged to engage the first disc
spring 47. The arcuate members 51 are arranged such that the first disc spring 47
can rotate with the input shaft 1 between the arcuate members 51 and such that axial
movement of the fork 46 parallel to the input shaft 1 moves the arcuate members 51
and hence the first disc spring 47 axially along the shaft if the first disc spring
47 is free to move, or biases the first disc spring 47 to move in the same direction
as the fork 46 if the first disc spring 47 is unable to move. The fork 46 has a second
pair of arcuate members 53 arranged to engage and act upon the second disc spring
49 in a similar manner.
[0040] The position of the fork 46 relative to the first and second gear wheels 3,5 can
be adjusted by movement of the selector rod 35 in the axial direction.
[0041] The inner edges of the first disc spring 47 are fixed to the bars 28 in the first
bar set 27 and the inner edges of the second disc spring 49 are fixed to the bars
30 in the second bar set 29. When the fork 46 moves, thereby moving or loading the
disc springs 47,49, the engagement bar sets 27,29 are likewise moved or biassed to
move.
[0042] The operation of the selector assembly 13 will now be described with reference to
Figures 5a-5f which for clarity illustrate diagrammatically the movement of the first
and second bar sets 27,29 by the relative positions of only one bar from each set.
[0043] Figure 5a shows the first and second bar sets 27,29 in a neutral position, that is,
neither bar set is engaged with a gear wheel. Figure 5b shows the first and second
bar sets moving into engagement with the first gear wheel 3 under the action of the
fork 46.
[0044] Figure 5c shows a condition when the first gear wheel 3 is fully engaged, that is,
the bars 28,30 are interleaved with the first group of dogs 19. The selector rod 35
is located such that the fork 46 maintains the first and second bar sets 27,29 in
engagement with the first gear wheel 3. Accordingly, power is transferred from the
input shaft 1, to the first gear wheel 3 by the first bar set 27 when decelerating
and the second bar set 29 when accelerating via the first group of dogs 19. Power
is transmitted to the output shaft 7 put via the third gear wheel 9.
[0045] Whilst accelerating (first gear wheel 3 rotating in the direction of arrow B in Figure
5c) using the first gear wheel pair 15, the engagement faces 43 of the bars of the
first bar set 27 are not loaded, whilst the engagement faces 43 of the bars of the
second bar set 29 are loaded. When a user, or an engine management system (not shown)
wishes to engage the second gear wheel pair 17, the selector rod 35 is moved such
that the fork 46 acts on the first disc spring 47, causing the bars of the first bar
set 27 to slide axially along the keyways 41 in the input shaft 1 thereby disengaging
the bars from the first gear wheel 3 (see Figure 5d).
[0046] The fork 46 also acts on the second disc spring 49 to bias the bars of the second
bar set 29 to move towards the second gear wheel 5. However, because the bars of the
second bar set 29 are loaded, i.e. are driving the first gear wheel 3, they cannot
be disengaged from the first gear wheel 3, and therefore the bars of the second bar
set 29 remain stationary.
[0047] When the bars of the first bar set 27 slide axially along the input shaft 1, the
engagement faces 43 engage the second group of dogs 21 (see Figure 5e). The bars then
begin to drive the second gear wheel 5 in the direction of Arrow C in Figure 5e and
energy is transmitted from the input shaft 1 to the output shaft 7 by way of the second
gear wheel pair 17. As this occurs, the bars of the second bar set 29 cease to be
loaded, and are free to disengage from the first group of dogs 19. Since the second
disc spring 49 is biassed by the fork 46, the bars of the second bar set 29 slide
axially along the keyways 41 in the input shaft 1 thereby completing the disengagement
of the first gear wheel 3 from the input shaft 1. The bars of the second bar set 29
slide along the keyways 41 in the input shaft until they engage the second gear wheel
5, thereby completing engagement of the second gear wheel 5 with the input shaft 1
(see Figure 5f). This method of selecting gear wheel pairs substantially eliminates
torque interruption since the second gear wheel pair 17 is engaged before the first
wheel pair 15 is disengaged, thus momentarily, the first and second gear wheel pairs
15,17 are simultaneously engaged.
[0048] When a gear wheel is engaged by both the first and second bar sets 27,29 it is possible
to accelerate or decelerate using a gear wheel pair with very little backlash occurring
when switching between the two conditions. Backlash is the lost motion experienced
when the dog moves from the engagement face 43 of the acceleration bar to the engagement
face 43 of the deceleration bar when moving from acceleration to deceleration, or
vice versa. A conventional dog-type transmission system has approximately 30 degrees
of backlash. A typical transmission system for a car in accordance with the current
invention has backlash of less than four degrees.
[0049] Backlash is reduced by minimising the clearance required between an engagement member
and a dog during a gear shift: that is, the clearance between the dog and the following
engagement member (see measurement 'A' in Figure 5b). The clearance between the dog
and the following engagement member is in the range 0.5mm - 0.03mm and is typically
less than 0.2mm. Backlash is also a function of the retention angle, that is, the
angle of the engagement face 43, which is the same as the angle of the undercut on
the engagement face of the dog. The retention angle influences whether there is relative
movement between the dog and the engagement face 43. The smaller the retention angle,
the less backlash that is experienced. The retention angle is typically between 2.5
and 15 degrees, and preferably is 15 degrees.
[0050] Transition from the second gear wheel pair 17 to the first gear wheel pair 15 whilst
decelerating is achieved by a similar process.
[0051] Whilst decelerating in the second gear wheel pair 17 the engagement surfaces 43 of
the bars of the first bar set 27 are not loaded, whilst the engagement surfaces 43
of the bars of the second bar set 29 are loaded. When a user, or an engine management
system (not shown) wishes to engage the first gear wheel pair 15, the selector rod
35 is moved such that the fork 46 slides axially relative to the input shaft 1. The
fork 46 acts on the first disc spring 47 attached to the first bar set 27, causing
the bars of the first bar set 27 to slide axially in the keyways 41 along the input
shaft 1 in the direction of the first gear wheel 3, thereby disengaging the first
bar set 27 from the second gear wheel 5.
[0052] The fork 5 also acts on the second disc spring 49 but since the bars of the second
bar set 29 are loaded, i.e. they are drivingly engaged with the dogs 21 on the second
gear wheel, the second bar set 29 remains stationary, however the second disc spring
49 is biassed by the fork 46 to move the second bar set 29 towards the first gear
wheel 3.
[0053] As the bars of the first bar set 27 slide axially in the keyways 41, the bars 28
engage the dogs 19 on the first gear wheel and begin to drive the first gear wheel
3 such that energy is transmitted from the input shaft 1 to the output shaft 7 by
way of the first gear wheel pair 15. As this occurs, the bars of the second bar set
29 cease to be loaded. The second disc spring 49 acts on the bars of the second bar
set 29, causing it to slide axially within the keyways 41 along the input shaft 1
towards the first gear wheel 3, thereby completing disengagement of the second gear
wheel 5. The second bar set 29 continues to slide within the keyways 41 along the
input shaft 1 until it engages the first gear wheel 3, thereby completing engagement
of the first gear wheel 3 with the input shaft 1.
[0054] Kick-down shifts, that is a gear shift from a higher gear ratio to a larger gear
ratio but where acceleration takes place, for example when a vehicle is travelling
up a hill and the driver selects a lower gear to accelerate up the hill, have a brief
torque interruption to allow disengagement prior to the shift.
[0055] A plurality of selector assemblies can be mounted on the input shaft with corresponding
pairs of gear wheels to provide a larger number of gear ratios between the output
shaft and the input shaft. It is also possible to have transmission systems with more
than two shafts to provide additional gear ratios.
[0056] Use of the transmission system leads to improved performance, lower fuel consumption
and lower emissions since drive interruption has substantially been eliminated. Also
the system is a more compact design than conventional gearboxes leading to a reduction
in gearbox weight.
[0057] The keyways 41 can be formed in a separate component from the input shaft which is
then fixedly attached to the input shaft, for example by using a splined arrangement.
The keyways 41 preferably have dovetailed profiles such that the bars are radially
restrained within the keyways (see Figure 5). Alternatively, the keyways can have
a slotted or T-shaped profile to radially restrain the bars. This provides a significant
advantage since it obviates the need for the first and second connector rings 37,39
to connect the bars together in the first and second bar sets. This arrangement is
preferred since it provides an improved means of restraining the radial position of
the bars 28,30 relative to the input shaft 1, leading to greater structural integrity
of the transmission system. Since the connector rings 37,39 are no longer required
it is possible to reduce the length of the engagement bars 28,30 thereby producing
more compact transmission systems.
[0058] Furthermore, it allows embodiments of the invention to be used having only one disc
spring 147 (see Figure 7) connecting all six bars together, i.e. bars from the first
and second sets, with the actuator arrangement being adapted accordingly. In use,
three of the bars would be loaded when the first gear is accelerating and three not
loaded, and moving the fork to bias the disc spring towards the second gear will move
the three unloaded bars out of engagement with the first gear wheel, leaving three
bars still in engagement. Once the bars have engaged with the second gear wheel, the
remaining three bars will disengage from the first gear wheel, and under the loading
of the disc spring move into engagement with the second gear wheel. This configuration
provides a highly compact arrangement leading to smaller, lighter gear boxes. The
axial space between the first and second gears to accommodate the selector mechanism
may be reduced to around 20mm for typical road car applications.
[0059] Figure 5a shows a recesses 28c in the top of each bar of the first bar set and a
recess 30c in the top of a bar from the second bar set. The recesses 28c,30c allow
connections to be made between the bars of the first and second bar sets 27,29 with
the arms of the first and second disc springs 47,49 respectively. The shape of the
recesses 28c,30c is such that the recesses allow each spring arm to move to a non-perpendicular
angle relative to the bars 28,30 during a gear shift.
[0060] The recesses 28c,30c shown in Figure 5a are for a two disc spring configuration.
For embodiments having only one disc spring 147 the recesses 28c,30c are located more
centrally along the length of the bars 28,30.
[0061] When a ring is not used to fix the positions of the bars in a set, the bars in a
set can move a small amount relative to each other in the axial direction. This is
because the only connection between the bars in a set is provided by a deformable
disc spring. A single bar is attached to each disc spring arm and each arm can deform
independently of the others, thereby allowing the relative movement between the bars.
The bars in a set will nevertheless essentially move in unison.
[0062] It will be appreciated by the skilled man that various modifications can be made
to the above embodiment that are within the scope of the current invention, for example
the number of dogs on each of the gear wheels is not limited to three, for example
any practicable number of dogs can be used. It has been found that two to eight dogs
are suitable for most applications. Similarly, the number of bars in a bar set can
be any practicable number but most preferably the number of bars in a set equals the
numbed of dogs in a group.
[0063] The transmission system can be used in any vehicle for example, road cars, racing
cars, lorries, motorcycles, bicycles, earth removal vehicles such as bulldozers, and
military vehicles. The system can also be used in any machine that has first and second
rotatable bodies wherein drive is to be transmitted from one of the rotatable bodies
to the other, for example in lathes and milling machines.
[0064] It will also be appreciated by the skilled person that the transmission system can
be adapted such that the selector assembly and the first and second gear wheels are
mounted on the output shaft and the fixed gear wheels are mounted on the input shaft.
1. A method for performing a kickdown shift in a transmission system including first
and second rotatable shafts (1,7), and means for transferring drive from one of the
shafts to the other shaft (1,7) including first and second gear wheels (3,5) each
rotatably mounted on the first shaft (1) and having drive formations (19) formed thereon,
a selector assembly (13) for selectively transmitting torque between the first shaft
(1) and the first gear wheel (3) and between the first shaft (1) and the second gear
wheel (5), wherein the selector assembly (13) includes an actuator assembly (31) and
first and second sets of engagement members (27,29) that are moveable into and out
of engagement with the first and second gear wheels (3,5) independently of each other,
said selector assembly (13) being arranged such that when a driving force is transmitted,
one of the first and second sets of engagement members (27,29) drivingly engages the
engaged gear wheel (3,5), and the other set of engagement members (27,29) is then
in an unloaded condition, wherein the actuator assembly (31) is arranged to move the
unloaded set of engagement members (27,29) into driving engagement with the unengaged
gear wheel (3,5) to effect a gear change, characterized in that the selector assembly (13) is arranged such that when the first and second sets of
engagement members (27,29) engage one of the first and second gear wheels (3,5) the
backlash between the first and second sets of engagement members and the drive formations
when moving between acceleration and deceleration is less than or equal to four degrees,
and by a brief torque interruption to allow disengagement prior to the shift.
2. A method according to claim 1, wherein the selector assembly is arranged such that
when a braking force is transmitted the first set of engagement members (27) drivingly
engages the engaged gear wheel, and the second set of engagement members (29) is in
an unloaded condition, and when a driving force is transmitted the second set of engagement
members (29) drivingly engages the engaged gear wheel, and the first set of engagement
members (27) is then in an unloaded condition.
3. A method according to claim 1 or 2, wherein the actuator assembly (31) is arranged
to bias the loaded set of engagement members towards the unengaged gear wheel without
disengaging the loaded set of engagement members from the engaged gear wheel.
4. A method according to any one of the preceding claims, wherein the first and second
sets of engagement members (27,29) are arranged to rotate, in use, with the first
shaft (1).
5. A method according to any one of the preceding claims, wherein the first shaft (1)
is an input shaft and the second shaft (7) is an output shaft and drive is transferred
from the input shaft to the output shaft.
6. A method according to any one of the preceding claims, wherein the drive formations
(19) on the first and second gear wheels (3,5) comprise first and second groups of
dogs (19) respectively.
7. A method according to claim 6, wherein the first and second groups of dogs (19) each
comprise between two and eight dogs, evenly distributed on the first and second gear
wheels (3,5) respectively.
8. A method according to claim 7, wherein the first and second groups of dogs (19) each
comprise between two and four dogs.
9. A method according to claim 8, wherein the first and second groups of dogs (19) each
comprise three dogs.
10. A method according to any one of the preceding claims, wherein the first and second
sets of engagement members (27,29) comprise between two and eight members.
11. A method according to claim 10, wherein the first and second sets of engagement members
(27,29) comprise between two and four members.
12. A method according to claim 11, wherein the first and second sets of engagement members
(27,29) comprise three members.
13. A method according to any one of the preceding claims, wherein the first shaft (1)
includes keyways (41) arranged such that the first and second sets of engagement members
(27,29) can slide axially along the keyways (41) and to radially restrain the positions
of the sets of engagement members (27,29).
14. A method according to claim 13, wherein the cross-section of the keyways (41) is one
of T-shaped, slotted, and dovetailed.
15. A method according to any one of the preceding claims, wherein the actuator assembly
(31) includes at least one resiliently deformable means (47,49;147) arranged to move
at least one of the first and second sets of engagement members (27,29) into engagement
with the first and second gear wheels (35) when the engagement members (27,29) are
in unloaded conditions.
16. A method according to claim 15, wherein the at least one resiliently deformable means
(47,49;147) is arranged to bias at least one of the first and second sets of engagement
members (27,29) towards the first or second gear wheel (3,5) when the engagement members
(27,29) are drivingly engaged with a gear wheel.
17. A method according to claims 15 or 16, wherein the actuator assembly (31) includes
first and second resiliently deformable means (47,49) connected to the first and second
sets of engagement members (27,29) respectively such that the first resiliently deformable
means (47) acts on the first set engagement members (27) and the second resiliently
deformable means (49) acts on the second set of engagement members (29).
18. A method according to claims 15 or 16, wherein the at least one resiliently deformable
means (147) is connected to the first and second sets of engagement members (27,29)
such that the resiliently deformable means (147) acts on both the first and second
sets of engagement members (27,29).
19. A method according to claim 15 to 18, wherein the members of the first and / or second
sets of engagement members (27,29) can perform limited axial movement relative to
each other in the keyways (41).
20. A method according to any one of claims 15 to 19, wherein the resiliently deformable
means (47,49;147) is a spring, and preferably a disc spring.
21. A method according to any one of claim to 20, wherein the disc spring includes a plurality
of arms, each arm having a first part that extends circumferentially around a portion
of the disc spring and a second part that extends substantially radially inwards.
22. A method according to any one of claims 15 to 21, wherein the actuator assembly (31)
includes a fork (46) that is arranged to engage the at least one resiliently deformable
means (47,49;147) to move the at least one resiliently deformable means (47,49;147)
axially along the first shaft (1).
23. A method according to any one of the preceding claims, wherein the drive formations
(19) are arranged such that they do not extend beyond the outside diameter of the
gear wheels.
1. Verfahren zum Durchführen eines Kick-down-Gangwechsels in einer Getriebeanlage, die
eine erste und eine zweite drehbare Welle (1, 7) und Mittel zum Übertragen eines Antriebs
von der einen der Wellen zu der anderen Welle (1, 7), die ein erstes und ein zweites
Zahnrad (3, 5) einschließen, die jeweils drehbar auf der ersten Welle (1) angebracht
sind und auf denselben geformte Antriebsformationen (19) haben, eine Schaltbaugruppe
(13) zum selektiven Übertragen eines Drehmoments zwischen der ersten Welle (1) und
dem ersten Zahnrad (3) und zwischen der ersten Welle (1) und dem zweiten Zahnrad (5)
einschließt, wobei die Schaltbaugruppe (13) eine Stellgliedbaugruppe (31) und einen
ersten und einen zweiten Satz von Eingriffselementen (27, 29), die unabhängig voneinander
in und außer Eingriff mit dem ersten und dem zweiten Zahnrad (3, 5) bewegt werden
können, einschließt, wobei die Schaltbaugruppe (13) derart angeordnet ist, dass, wenn
eine Antriebskraft übertragen wird, entweder der erste oder der zweite Satz von Eingriffselementen
(27, 29) antreibend das in Eingriff genommene Zahnrad (3, 5) in Eingriff nimmt und
sich der andere Satz von Eingriffselementen (27, 29) dann in einem unbelasteten Zustand
befindet, wobei die Stellgliedbaugruppe (31) dafür angeordnet ist, den unbelasteten
Satz von Eingriffselementen (27, 29) in einen Antriebseingriff mit dem nicht in Eingriff
genommenen Zahnrad (3, 5) zu bewegen, um einen Gangwechsel zu bewirken, dadurch gekennzeichnet, dass die Schaltbaugruppe (13) derart angeordnet ist, dass, wenn der erste und der zweite
Satz von Eingriffselementen (27, 29) entweder des erste oder das zweite Zahnrad (3,
5) in Eingriff nehmen, das Spiel zwischen dem ersten und dem zweiten Satz von Eingriffselementen
und den Antriebsformationen, wenn sie sich zwischen Beschleunigung und Verzögerung
bewegen, geringer als oder gleich vierzig Grad ist, und durch eine kurze Drehmomentunterbrechung,
um vor dem Gangwechsel ein Ausrücken zu ermöglichen.
2. Verfahren nach Anspruch 1, wobei die Schaltbaugruppe derart angeordnet ist, dass,
wenn eine Bremskraft übertragen wird, der erste Satz von Eingriffselementen (27) antreibend
das in Eingriff genommene Zahnrad in Eingriff nimmt und sich der zweite Satz von Eingriffselementen
(29) in einem unbelasteten Zustand befindet, und wenn eine Antriebskraft übertragen
wird, der zweite Satz von Eingriffselementen (29) antreibend das in Eingriff genommene
Zahnrad in Eingriff nimmt und sich der erste Satz von Eingriffselementen (27) dann
in einem unbelasteten Zustand befindet.
3. Verfahren nach Anspruch 1 oder 2, wobei die Stellgliedbaugruppe (31) dafür angeordnet
ist, den belasteten Satz von Eingriffselementen zu dem nicht in Eingriff genommenen
Zahnrad hin vorzuspannen, ohne den belasteten Satz von Eingriffselementen von dem
in Eingriff genommenen Zahnrad auszurücken.
4. Verfahren nach einem der vorhergehenden Ansprüche, wobei der erste und der zweite
Satz von Eingriffselementen (27, 29) dafür angeordnet sind, sich, bei Anwendung, mit
der ersten Welle (1) zu drehen.
5. Verfahren nach einem der vorhergehenden Ansprüche, wobei die erste Welle (1) eine
Antriebswelle ist und die zweite Welle (7) eine Abtriebswelle ist und der Antrieb
von der Antriebswelle zu der Abtriebswelle übertragen wird.
6. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Antriebsformationen (19)
auf dem ersten und dem zweiten Zahnrad (3, 5) eine erste und eine zweite Gruppe von
Mitnehmern (19) umfassen.
7. Verfahren nach Anspruch 6, wobei die erste und die zweite Gruppe von Mitnehmern (19)
jeweils zwischen zwei und acht Mitnehmern umfassen, die jeweils gleichmäßig auf dem
ersten bzw. dem zweiten Zahnrad (3, 5) verteilt sind.
8. Verfahren nach Anspruch 7, wobei die erste und die zweite Gruppe von Mitnehmern (19)
jeweils zwischen zwei und vier Mitnehmern umfassen.
9. Verfahren nach Anspruch 6, wobei die erste und die zweite Gruppe von Mitnehmern (18)
jeweils drei Mitnehmer umfassen.
10. Verfahren nach einem der vorhergehenden Ansprüche, wobei der erste und der zweite
Satz von Eingriffselementen (27, 29) zwischen zwei und acht Elementen umfassen.
11. Verfahren nach Anspruch 10, wobei der erste und der zweite Satz von Eingriffselementen
(27, 29) zwischen zwei und vier Elementen umfassen.
12. Verfahren nach Anspruch 11, wobei der erste und der zweite Satz von Eingriffselementen
(27, 29) drei Elemente umfassen.
13. Verfahren nach einem der vorhergehenden Ansprüche, wobei die erste Welle (1) Keilnuten
(41) einschließt, die derart angeordnet sind, dass der erste und der zweite Satz von
Eingriffselementen (27, 29) in Axialrichtung längs der Keilnuten (41) gleiten können
und dass sie die Positionen der Sätze von Eingriffselementen (27, 29) in Radialrichtung
einschränken.
14. Verfahren nach Anspruch 13, wobei der Querschnitt der Keilnuten (41) entweder, T-förmig,
geschlitzt oder schwalbenschwanzförmig ist.
15. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Stellgliedbaugruppe (31)
wenigstens ein elastisch verformbares Mittel (47, 49; 147) einschließt, das dafür
angeordnet ist, wenigstens den ersten und/oder den zweiten Satz von Eingriffselementen
(27, 29) in einen Eingriff mit dem ersten und dem zweiten Zahnrad (3, 5) zu bewegen,
wenn sich die Eingriffselemente (27, 29) in einem unbelasteten Zustand befinden.
16. Verfahren nach Anspruch 15, wobei das wenigstens eine elastisch verformbare Mittel
(47, 49; 147) dafür angeordnet ist, wenigstens den ersten und/oder den zweiten Satz
von Eingriffselementen (27, 29) zu dem ersten oder dem zweiten Zahnrad (3, 5) hin
vorzuspannen, wenn die Eingriffselemente (27, 29) antreibend mit einem Zahnrad in
Eingriff gebracht sind.
17. Verfahren nach Anspruch 15 oder 16, wobei die Stellgliedbaugruppe (31) ein erstes
und ein zweites elastisch verformbares Mittel (47, 49) einschließt, die jeweils mit
dem ersten bzw. dem zweiten Satz von Eingriffselementen (27, 29) verbunden sind derart,
dass das erste elastisch verformbare Mittel (47) auf den ersten Satz von Eingriffselementen
(27) einwirkt und das zweite elastisch verformbare Mittel (49) auf den zweiten Satz
von Eingriffselementen (29) einwirkt.
18. Verfahren nach Anspruch 15 oder 16, wobei das wenigstens eine elastisch verformbare
Mittel (147) mit dem ersten und dem zweiten Satz von Eingriffselementen (27, 29) verbunden
ist derart, dass das elastisch verformbare Mittel (147) sowohl auf den ersten als
auch auf den zweiten Satz von Eingriffselementen (27, 29) einwirkt.
19. Verfahren nach Anspruch 15 bis 18, wobei die Elemente des ersten und/oder des zweiten
Satzes von Eingriffselementen (27, 29) in den Keilnuten (41) eine begrenzte axiale
Bewegung im Verhältnis zueinander ausführen können.
20. Verfahren nach einem der Ansprüche 15 bis 19, wobei das elastisch verformbare Mittel
(47, 49; 147) eine Feder und vorzugsweise eine Tellerfeder ist.
21. Verfahren nach einem der Ansprüche 15 bis 20, wobei die Tellerfeder mehrere Arme einschließt,
wobei jeder Arm einen ersten Teil, der sich umlaufend um einen Abschnitt der Tellerfeder
erstreckt, und einen zweiten Teil, der sich im Wesentlichen in Radialrichtung nach
innen erstreckt, hat.
22. Verfahren nach einem der Ansprüche 15 bis 21, wobei die Stellgliedbaugruppe (31) eine
Gabel (46) einschließt, die dafür angeordnet ist, das wenigstens eine elastisch verformbare
Mittel (47, 49; 147) in Eingriff zu nehmen, um das wenigstens eine elastisch verformbare
Mittel (47, 49; 147) in axialer Richtung längs der ersten Welle (1) zu bewegen.
23. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Antriebsformationen (19)
derart angeordnet sind, dass sie sich nicht über den Außendurchmesser der Zahnräder
hinaus erstrecken.
1. Procédé pour réaliser une rétrogradation forcée dans un système de transmission comprenant
des premier et second arbres rotatifs (1, 7) et des moyens pour transférer l'entraînement
de l'un des arbres à l'autre arbre (1, 7) comprenant des première et seconde roues
dentées (3, 5), chacune montée de manière rotative sur le premier arbre (1) et ayant
des formations d'entraînement (19) formées sur celles-ci, un ensemble de sélecteur
(13) pour transmettre sélectivement le couple entre le premier arbre (1) et la première
roue dentée (3) et entre le premier arbre (1) et la seconde roue dentée (5), dans
lequel l'ensemble de sélecteur (13) comprend un ensemble d'actionneur (31) et des
premier et second ensembles d'éléments de mise en prise (27, 29) qui sont mobiles
dans et hors de mise en prise avec les première et seconde roues dentées (3, 5) indépendamment
l'un de l'autre, ledit ensemble de sélecteur (13) étant agencé de sorte que lorsqu'une
force d'entraînement est transmise, l'un des premier et second ensembles d'éléments
de mise en prise (27, 29) met en prise par entraînement la roue dentée (3, 5) mise
en prise, et l'autre ensemble d'éléments de mise en prise (27, 29) est ensuite dans
une condition non chargée, dans laquelle l'ensemble d'actionneur (31) est agencé pour
déplacer l'ensemble non chargé d'éléments de mise en prise (27, 29) en mise en prise
par entraînement avec la roue dentée dégagée (3, 5) afin d'effectuer un changement
de vitesse, caractérisé en ce que l'ensemble de sélecteur (13) est agencé de sorte que lorsque les premier et second
ensembles d'éléments de mise en prise (27, 29) mettent en prise l'une parmi les première
et seconde roues dentées (3, 5), le jeu entre les premier et second ensembles d'éléments
de mise en prise et les formations d'entraînement lors du mouvement entre l'accélération
et la décélération, est inférieur ou égal à quatre degrés, et par une brève interruption
de couple pour permettre le dégagement avant le passage de la vitesse.
2. Procédé selon la revendication 1, dans lequel l'ensemble de sélecteur est agencé de
sorte que lorsqu'une force de freinage est transmise, le premier ensemble d'éléments
de mise en prise (27) met en prise par entraînement la roue dentée mise en prise,
et le second ensemble d'éléments de mise en prise (29) est dans une condition non
chargée, et lorsqu'une force d'entraînement est transmise, le second ensemble d'éléments
de mise en prise (29) met en prise par entraînement la roue dentée mise en prise,
et le premier ensemble d'éléments de mise en prise (27) est ensuite dans une condition
non chargée.
3. Procédé selon la revendication 1 ou 2, dans lequel l'ensemble d'actionneur (31) est
agencé pour solliciter l'ensemble chargé d'éléments de mise en prise vers la roue
dentée dégagée sans dégager l'ensemble chargé d'éléments de mise en prise de la roue
dentée mise en prise.
4. Procédé selon l'une quelconque des revendications précédentes, dans lequel les premier
et second ensembles d'éléments de mise en prise (27, 29) sont agencés pour tourner,
à l'usage, avec le premier arbre (1).
5. Procédé selon l'une quelconque des revendications précédentes, dans lequel le premier
arbre (1) est un arbre d'entrée et le second arbre (7) est un arbre de sortie et l'entraînement
est transféré de l'arbre d'entrée à l'arbre de sortie.
6. Procédé selon l'une quelconque des revendications précédentes, dans lequel les formations
d'entraînement (19) des première et seconde roues dentées (3, 5) comprennent des premier
et second groupes de crabots (19) respectivement.
7. Procédé selon la revendication 6, dans lequel les premier et second groupes de crabots
(19) comprennent chacun entre deux et huit crabots, répartis régulièrement sur les
première et seconde roues dentées (3, 5) respectivement.
8. Procédé selon la revendication 7, dans lequel les premier et second groupes de crabots
(19) comprennent chacun entre deux et quatre crabots.
9. Procédé selon la revendication 8, dans lequel les premier et second groupes de crabots
(19) comprennent chacun trois crabots.
10. Procédé selon l'une quelconque des revendications précédentes, dans lequel les premier
et second ensembles d'éléments de mise en prise (27, 29) comprennent entre deux et
huit éléments.
11. Procédé selon la revendication 10, dans lequel les premier et second ensembles d'éléments
de mise en prise (27, 29) comprennent entre deux et quatre éléments.
12. Procédé selon la revendication 11, dans lequel les premier et second ensembles d'éléments
de mise en prise (27, 29) comprennent trois éléments.
13. Procédé selon l'une quelconque des revendications précédentes, dans lequel le premier
arbre (1) comprend des rainures de clavette (41) agencées de sorte que les premier
et second ensembles d'éléments de mise en prise (27, 29) peuvent coulisser axialement
le long des rainures de clavette (41) et afin de limiter radialement les positions
des ensembles d'éléments de mise en prise (27, 29).
14. Procédé selon la revendication 13, dans lequel la section transversale des rainures
de clavette (41) est l'une parmi une forme de T, fendue et en forme de queue d'aronde.
15. Procédé selon l'une quelconque des revendications précédentes, dans lequel l'ensemble
d'actionneur (31) comprend au moins un moyen élastiquement déformable (47, 49 ; 147)
agencé pour déplacer au moins l'un parmi les premier et second ensembles d'éléments
de mise en prise (27, 29) en mise en prise avec les première et seconde roues dentées
(35) lorsque les éléments de mise en prise (27, 29) sont dans des conditions non chargées.
16. Procédé salon la revendication 15, dans lequel le au moins un moyen élastiquement
déformable (47, 49 ; 147) est agencé pour solliciter au moins l'un parmi les premier
et second ensembles d'éléments de mise en prise (27, 29) vers la première ou la seconde
roue dentée (3, 5), lorsque les éléments de mise en prise (27, 29) sont mis en prise
par entraînement avec une roue dentée.
17. Procédé selon la revendication 15 ou 16, dans lequel l'ensemble d'actionneur (31)
comprend des premier et second moyens élastiquement déformables (47, 49) raccordés
aux premier et second ensembles d'éléments de mise en prise (27, 29) respectivement,
de sorte que le premier moyen élastiquement déformable (47) agit sur le premier ensemble
d'éléments de mise en prise (27) et le second moyen élastiquement déformable (49)
agit sur le second ensemble d'éléments de mise en prise (29).
18. Procédé selon la revendication 15 ou 16, dans lequel le au moins un moyen élastiquement
déformable (147) est raccordé aux premier et second ensembles d'éléments de mise en
prise (27, 29) de sorte que le moyen élastiquement déformable (147) agit à la fois
sur les premier et second ensembles d'éléments de mise en prise (27, 29).
19. Procédé selon les revendications 15 à 18, dans lequel les éléments des premier et/ou
second ensembles d'éléments de mise en prise (27, 29) peuvent réaliser un mouvement
axial limité les uns par rapport aux autres dans les rainures de clavette (41).
20. Procédé selon l'une quelconque des revendications 15 à 19, dans lequel le moyen élastiquement
déformable (47, 49 ; 147) est un ressort, et de préférence un ressort à disques.
21. Procédé selon la revendication 20, dans lequel le ressort à disques comprend une pluralité
de bras, chaque bras ayant une première partie qui s'étend de manière circonférentielle
autour d'une partie du ressort à disque et une seconde partie qui s'étend sensiblement
radialement vers l'intérieur.
22. Procédé selon l'une quelconque des revendications 15 à 21, dans lequel l'ensemble
d'actionneur (31) comprend une fourche (46) qui est agencée pour mettre en prise le
au moins un moyen élastiquement déformable (47, 49 ; 147) pour déplacer le au moins
un moyen élastiquement déformable (47, 49 ; 147) axialement le long du premier arbre
(1).
23. Procédé selon l'une quelconque des revendications précédentes, dans lequel les formations
d'entraînement (19) sont agencées de sorte qu'elles ne s'étendent pas au-delà du diamètre
externe des roues dentées.
REFERENCES CITED IN THE DESCRIPTION
This list of references cited by the applicant is for the reader's convenience only.
It does not form part of the European patent document. Even though great care has
been taken in compiling the references, errors or omissions cannot be excluded and
the EPO disclaims all liability in this regard.
Patent documents cited in the description